Overflow box question

[ashnat]

I installed an overflow box and a sump on my 55gal reef tank 2 months ago. The overflow box is rated for 600gph and I bought a return pump that is right around 650gph for the 3-4ft of head that it is pumping against. However, about every 2-3 days an air bubble starts to build up in the u-tube section and the overflow rate drops. I end up having to suck the air bubble out through the siphon starter hose to get the flow back up. Does anyone know what I need to do to fix this problem.

Thanks

 

[sjm817]

Sounds like something is restricting return flow. It doesn't take much to keep a U Tube clear of bubbles. Maybe 200 GPH or so. What is the model of the overflow and return pump? How do you have them plumbed?

 

[ashnat]

My return pump is a Rio pump and the overflow box I bought on e-bay but I don't remember the name. I built a Hofer gurgle buster to reduce the noise of the drain pipe and it works well. Couldn't fit a durso stand pipe in it. I can adjust the Hofer gurgle buster pipe to allow more or less flow but the problem always seems to be that the air bubble builds and if I get rid of it the flow picks up again.

 

[Blown 346]

Every now and then I will get some air bubbles in mine, I just wiggle the U tube and or pick it up slightly and slam it down, and the bubbles will get sucked thru.

 

[petermai]

i have the cpr with a little nipple on top that is connected to the overhead to draw out the bubbles. you should try the same thing. just drill a small hole on top at the arc of the siphon tube and attach airline tubing conneccting it to a power head. this will also work as an automatic primer. good luck.

 

[graveyardworm]

You need more flow. With enough flow the bubbles will shoot right through. What model rio pump are you using?

 

[sjm817]

Is the U Tube bend smooth, or more like an accordion? I've had a couple of U Tube overflows (Amiracle and Lifereef). Neither have ever accumulated a single bubble at the top even when running low flow through them.

What model Rio? Can you take a pic of the overflow?

 

[drowningdreamer]

My overflow box has been up for about a month. Would have had it up long ago but was working on sump. Finally just did the rubbermaid way for now. Heres a pic of box and as you can see it has the bumpy bend on the U-tube. Also there is some algae on and in the tube but havn't had any problems yet. Using mag 9.5 to pump water back to tank.

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[Mykayel]

You must not have enough flow. The flow through your overflow cannot "slow down" as you say otherwise your tank would spill over the top as your return pump would still be pumping the same amount of water.

The overflow I have has the little ridges on the u-tube just like the one pictured above and bubles go right through it. I've even started the syphon with a huge air bubble at the top and the flow just pushes it through. Its all a matter of flow. You just don't have enough flow.

 

[Fast Fred]

Dittos to what Petermai said. An air nipple at the top of the U-tube connected to a powerhead in the tank.

 

[ashnat]

My Rio pump is a 1700 and has a lot of flow. I suppose I should check the rate but I don't believe it is a problem. When I referred to the u-tube it is not actually a tube but a full width u built into the box. It has the hole on top with an air line connected which is what I use to start the siphon. My tank doesn't ever start to overflow or anything but the water level will get to where it is about an inch above the overflow inside the tank and then the scum layer starts to build up on the surface of the water.

I'll do a little test to see what flow rate I am getting from my pump.

Thanks

 

[ashnat]

Ok, I drew down the level in my tank and then started my pump and found that I am only getting about 220gph. I have a 1 inch return line that tees off to two 5/8 inch lines feeding my two 1/2 inch sea-swirls. Have I plumbed it up wrong?

 

[sjm817]

<a href=showthread.php?s=&postid=6723637#post6723637 target=_blank>Originally posted</a> by ashnat
My Rio pump is a 1700 and has a lot of flow. I suppose I should check the rate but I don't believe it is a problem. When I referred to the u-tube it is not actually a tube but a full width u built into the box. It has the hole on top with an air line connected which is what I use to start the siphon. My tank doesn't ever start to overflow or anything but the water level will get to where it is about an inch above the overflow inside the tank and then the scum layer starts to build up on the surface of the water.

I'll do a little test to see what flow rate I am getting from my pump.

Thanks

That explains it. It is a CPR style overflow. That is an inherent design problem. No amount of flow will fix it. In fact, increasing the flow will make it worse. Your only option other than replacing it is to connect a vacuum pump to the air fitting and leave it running continuously. The Aqualifter pump works well for this.

 

[integlikewhoa]

Rio's are crap too. There has been alot of known problem with them. I would recommend getting rid of that too.